(a) Field of the Invention
This invention generally relates to a tool holder for a turret lathe, and more particularly, but not by way of limitation, to a turret lathe tool holder which uses a collet for adjustment and support of the tool.
(b) Discussion of Known Art
Turret lathes are particularly well known manufacturing machines which have been favored for production runs due to the high production rates that are achievable with the use of a turret lathe. These high production rates due in large part to the fact that the operations to be carried out on the workpiece can be changed by a simple rotation of the turret that supports the tools being used. The turret typically includes several faces which include means for indexing tools to be mounted on the face.
A well recognized problem with turret lathes is that the setup time to mount the required tools and to position the workpiece can be relatively long. The tools to be mounted on the individual faces of the turret are typically fastened or bolted against the facet on the turret through a tool support which includes a split bore which accepts a bushing, which in turn accepts the tool to be supported on the turret.
The bushing used to accept the tool must be machined to match the shank of the specific tool that is to be used. This means that the bushing must be made to match the split bore in the tool support as well as the diameter of the tool. Once the bushing has been prepared, the shank of the tool is inserted into the bushing, and then the bushing, together with the tool, is inserted into the bore of the tool support. The split in the bore of the tool support typically includes fasteners which extend through the split and which are used to tighten the split bore around the bushing and tool shank assembly. This known method for supporting the tool presents some significant disadvantages to the user of the turret lathe.
One significant disadvantage, aside from the disadvantage of having to make a customized bushing, is that the fastening of the bushing into the split bore of the support will necessarily hold the bushing at a location that is slightly off center from the central axis of the bore. An example of a tool support which includes a split bore is illustrated in U.S. Pat. No. 5,063,799 to Brewer. FIG. 1 of the Brewer patent, incorporated herein by reference, illustrates the structure of known tool holders. The split bore which is used to support the bushing will necessarily bias one side of the bore towards the opposing side, squeezing the bushing between the sides of the split bore. Accordingly, to be able to provide some sort of clamping force to the bushing, the gap created by the split on the bore will necessarily produce an oblong aperture once closed. Moreover, the closing of the gap to squeeze the bushing will also result in positioning of the centerline of the tool shank and the bushing at a location that is slightly offset from the of the split bore in its undeformed state.
Other turret lathe tool gripping devices include the device described in U.S. Pat. No. 2,833,546, which includes a revolving turret that mounts into tailstock of a conventional lathe to enable the user to quickly change the tool used against the workpiece.
Another tool support device is taught in U.S. Pat. No. 5,080,536 to Andrews, which agin follows conventional tool support conventions by providing a bushing with a split bore that is squeezed transversely to accommodate the diameter of the shank of the tool to be supported. The transverse force approach is also illustrated in U.S. Pat. No. 2,369,209 to Bullard, 3d., et al.
The radial clamping action of collets is well known. The application of collets as supports for tools, however, has been limited to the use of the collet in chucks and the like, where a rotating tool, such as a drill bit is being rotated and driven into the workpiece. For example, in U.S. Pat. No. 5,522,605 Lewis et al., a collet based chuck for holding a drill bit is described. However, the Lewis patent does not provide guidance as to how a collet could be used to support a cutting tool, particularly a stationary cutting tool that is supported against the turret of a turret lathe. Importantly, the Lewis patent does not provide any suggestion as to whether it would be desirable to use a collet in anything other than a chuck. Similarly, U.S. Pat. No. 4,817,972 to Kubo, and U.S. Pat. No. 2,337,471 to Hines discuss the desirability of collets in rotating tool supports such as chucks.
Thus, a review of known tool supports reveals that the use of an transverse, or non-radial, force to grip a stationary tool is widely accepted. Examples of this approach at gripping tools are found in U.S. Pat. No. 5,214,989 to Giannetti, U.S. Pat. No. 4,890,523 to Satran.
Therefore, a review of known devices reveals that there remains a need for a simple device that can reliably support a tool against a turret on a turret lathe, without introducing the distortions of a transversely gripping device.
Still further, there remains a need for a tool gripping device for a turret lathe, the tool gripping device obviating the need for an intermediary bushing that is to be held by the tool support.
Even further yet, there remains a need for a tool support for a turret lathe, wherein the tool support does not protrude excessively from the turret, as for example if a conventional chuck were to be used to support a tool from the turret.